Holographic correction of aberrated optical elements has been demonstrated in the prior art. The adaptation of this technique for correcting large optical components for telescopes was first suggested in 1971. The basic principle has not changed much since then, with only minor variations in the method by which this correction is achieved. The main emphasis of such research however, has been to use these holographically corrected telescopes (HCTs) for imaging, lidar (light ranging and detection) or directed energy weaponry. However, there has been no suggestion in the prior art that this device could be used for other purposes such as in data communications.
Data transmission relies on the modulation of an electromagnetic carrier wave broadcast by a suitable antenna to a receiving antenna where the signal is demodulated and the information extracted. Most communications networks broadcast through the atmosphere or in space use radio or microwave frequencies because it is easy to modulate these carrier waves and they are largely unaffected by weather. Unfortunately, due to diffraction of these large waves, even emitters several meters in size tend to scatter the broadcast signal over a large area. This spreading of the signal wastes much of the signal power as well as reducing the Signal to Noise Ratio (SNR) at the receiver. The SNR is a measure of the strength of the received carrier wave compared to the random emissions at the same frequency coming from other sources. It is important to have a large SNR so that the desired information can be separated from signals that do not come from the transmitter. The SNR depends heavily on the size of the transmitter and receiver as well as the frequency of the carrier wave.
Ideally, a communications network would utilize infrared, optical or UV frequencies, which are much higher than radio or microwave frequencies. At these wavelengths, a signal diffracts less, which means a beam can be transmitted with much less spread, resulting in less wasted power, a more secure transmission, and a higher SNR. The higher frequencies also means that the signal can be modulated at a much higher rate allowing for higher data bandwidths and hence a larger amount of data over a given channel in a specific period of time. This is the reason that optical fiber communications have gained so much prominence in recent years.
One of the major problems with optical communications has been that the receiver and transmitter optics must have a very accurate surface figure—to a fraction of the wavelength of the radiation used. At radio and microwave frequencies where the wavelengths are anywhere from 1 cm to 1 m, it is relatively simple to manufacture a dish (or telescope) which has a surface quality at this tolerance. At infrared and optical wavelengths, however, where the wavelengths are around a micron (a millionth of a meter), it is expensive to fabricate large telescopes to these specifications. For a space-based network of communications satellites, there is the added problem of ensuring that the mirrors maintain their high surface quality during launch, deployment and lifetime in a thermally stressful environment.
Accordingly, there is need and market for an optical data communication system that overcomes the above prior art shortcomings.
There has now been discovered a method for data communication of clarity of transmision employing optics of low cost.